Histological, physiological and biochemical studies are being conducted on spinal rats to determine why regenerative processes are so limited in the injured spinal cord. (1) Improved histological and histochemical techniques have been developed and are being applied in a histopathological study of the transected spinal cord of rats. (2) Enzyme treatments are being used to test the validity of a report from the Soviet Union that application of trypsin and hyaluronidase at the site of transection results in nerve regeneration and functional restitution. (3) When a portion of the nerve fibers supplying a discrete region of spinal cord or muscle are transected, the residual intact fibers sprout collateral outgrowths which can restore a certain measure of function to the injured tissue. Experiments have been designed to elucidate the factors responsible for this process in mammalian muscle. (IV) Biochemical techniques for studying the specificity with which neural connections are established in the normal central nervous system will be developed with the aim of applying these methods to the study of the injured spinal cord.